1. Technical Field of the Invention
The present invention relates to a printing device, a production unit, and a production method of electronic parts, which perform a resin encapsulation having a voidless precise shape of the electronic parts, the forming of a solder bump, the hole-plugging of a substrate or dispensing and the like.
2. Description of the Related Art
A conventional technology is disclosed in the following documents. For example, as a conventional packaging technology, it is well known that an integrated circuit formed on a work piece is encapsulated (packaged). While the mainstream of such technology is a transfer molding method, as a method of using a plastic material comprising liquid synthetic resin, a dispenser method and a printing method are generally known. As for the printing method, a method of de-gassing by performing an atmospheric printing and a vacuum differential pressure printing method are commonly known. For a ceramic substrate, the vacuum differential pressure printing method is mainly adopted. With respect to the plastic material substrate, though this method is partially adopted and its usage is gradually growing, because of various problems involved, the method has not yet taken root in the industry. Further, the method is also applied to the CSP production process of a wafer level or its encapsulation. From now onward, since shifting to complexity, three dimensions, or built-in substrates of the electronic parts are promoted, there is a demand for an encapsulation method having a voidless precision-shape.
Patent Document 1: Japanese Patent No 3198273
Patent Document 2: Japanese Patent No 3084440
Patent Document 3: Japanese Patent Application No. 2001-331497 (Laid-open Publication No. 2003-133739)
Patent Document 4: Japanese Patent No. 3113974
Patent Document 5: Japanese Patent No. 2873501
Patent Document 6: Japanese Patent Application Laid-Open Publication No. 5-90271
Patent Document 7: Japanese Patent Application Laid-Open Publication No. 10-34878
Patent Document 8: Japanese Patent Application Laid-Open Publication No. 2001-232758
Patent Document 9: Japanese Patent Application Laid-Open Publication No. 2001-232765
Non-Patent Document 1: “Electronic Journal”, April 2003, pp. 122-124. “Bump Forming Device for lead-free soldering”.
With respect to the solder bump formation, the printing method has recently come to draw attention as against a conventional transfer method. An important technology is how quantitatively a high viscose solder paste is voidlessly filled into a perforated plate having a high aspect ratio by corresponding to a narrow pitching shift, and various techniques have been proposed. With respect to the head of the printing device using an atmospheric printing machine, such a type as performing a printing or being filled by an open type squeegee, an encapsulated type squeegee, a press-fit type squeegee, and a roller press-fit type squeegee is introduced. Further, there is also a method in which a photosensitive dry film is laminated by the bump formation of a wafer so as to form a via, and a solder paste is filled by the printing method, and a bump is formed by reflowing, thereby peeling off a film.
For the hole-plugging of vias and through holes of the printed circuit board and a wafer substrate a conductive paste and a non-conductive paste are used, and there is a hole-plugging method by the atmospheric printing or a vacuum difference pressure printing method using a squeegee. A development which seeks for a simpler and lower cost process by a mass lamination method is under way. In the printing method of the conductive paste, the development of the paste by aiming at improvement of electrical performance and reliability is promoted. Although the vacuum printing method of filling the paste voidlessly and simply into various vias is going into practical use, since there are defects such as the device being on a grand scale, and the productivity thereof being low, the modification thereof is solicited. Further, the plugging of the through hole is performed by using a mask and a jig in such a way that the work piece is positioned and filled with resin, and further, a plug is formed on the upper surface and the lower surface of the work, and then, it is cured, and both surfaces of the work is polished and made flat.
A principle of printing a high viscose resin flatly in a shape having a clearance gap by a squeegee by using a perforated plate is not established. As shown in FIG. 15(A), a resin m having adhered to a squeegee 60 and a work piece 2 has vertically clearance gaps at an opening portion 103 of a perforated plate 1, and a velocity gradient is generated for the movement of the squeegee 60, and the rear resin m is drawn out so as to be printed several tens μ thinner than a prescribed thickness. This is a resin feeding method not influenced by viscosity and clearance gap.
At the end edge of the opening portion 103 of the perforated plate 1, as shown in FIG. 15(B), the resin m pressed by the squeegee 60 is stemmed at the end portion of the opening portion 103, and is further pressurized and released at the passing time of the squeegee 60 so as to be printed several tens μ thicker than a prescribed thickness. This is a method of maintaining a filling pressure of the top end portion of the squeegee unchanged all the time regardless of the shape of the mask and the work piece 2.
The opening portion 103 of the perforated plate 1 shown in FIG. 15 and, though not shown, a printing starting portion of a groove between chips within the opening portion 103 are not capable of achieving a filling pressure of the squeegee 60, and end up being unfilled or cannot print but only thinly, thereby creating a void generating cause. The liquid resin due to the above described three factors is unable to be printed in a precise shape, and though a countermeasure was forcibly taken by futile operations of the shape of the mask and squeegee 60 in addition to a low viscosity of resin by sacrificing the reliability, a basic solution has not been reached. This is a resin feeding method having a strong filling force not affected by the shape of a printing portion.
The high-viscosity resin, which is wire-bonded in high density by encapsulation of BGA and CSP such as a lamination type and the like in a state in which a net is put up and is fed with a filler and the like at a high percentage, can be hardly filled by a squeegee function. Hence, when the resin is printed in the vacuum and is applied with a vacuum differential pressure, though a filling efficiency can be expected to some extent, there exists no mechanism to remove the residual void, and the void is miniaturized and dispersed and remains. Basically, before the differential pressure is applied, it is a necessary condition that the resin fills a cavity and pushes out the air. An extremely thin package has a wire close to its surface, and is short-circuited with the cavity with no differential pressure generated, and is at high risk of generating a void. Further, the packaging three-dimensionally laminated is wire-bonded in high density and moreover is Philip-chipped, and a filling is required even in microgaps, and therefore, a method having a strong filling function and capable of a precise printing is indispensable. Further, with respect to the building of the electronic parts into the substrate, a voidless filling of the liquid resin and a coating of a uniform thickness are required. This is excellent filling and voidless filling methods not affected by viscosity.
In case the vias of the wafer substrate and the laminated substrate are filled with various resins, a strong printing pressure is required, and due to inroad of the squeegee and viscosity of the resins, the resins are scooped out from the vias, and moreover, are contracted by curing. To prevent this from occurring, by using various masks, a precise positioning of the masks is made, and the resin is filled into them and interpolated, but a convex solid plug is formed, and the polishing of such a plug entails great difficulties. This is a hole-plugging method in which a filling is directly made on the work piece 2 without having a perforated plate, a precise positioning device, and a cleaning device at all, and which can cover a concave portion and a shrinkage of the resin voidlessly, and can limit a polishing working process to the minimum possible.
Specifically, a mask is positioned on the upper surface of the work, and at the bottom thereof, a jig to form a plug is positioned, and a printing is performed so that a plug (convex printing) is formed on both sides of the work, and this plug is cured and polished. In this case, the holes having different diameters are separated and printed, and curing-polishing is performed for every hole diameter. Further, because of shifting to the miniaturization and a large scale substrate, the position of the pattern of the mask and the position of the pattern of the work are not matched due to elongation of a mask and elongation of a work caused by polishing, and there are often the cases where the printing is required twice. When the plug is formed, a polishing thereof entails difficulties, and a device is required in which it is difficult to uniformly polish the plug and a copper plating and control the thickness and elongation thereof. When voidlessness is required, it necessitates a printing in the vacuum, and when the mask exists, a device comprising a positioning, a cleaning and the like is required, and such a device becomes large-sized like a plant and expensive, and moreover, becomes low in productivity. Hence, a plugging method of forming a plug voidless without using the jig and the mask, and capable of simultaneously filling the holes of different diameters and limiting the working process to the minimum possible is required.
Solder paste printing methods by the bump formation of the solder according to Japanese Patent Application Laid-Open Publication No. 2001-232758 and Japanese Patent Application Laid-Open Publication No. 10-34878 have been proposed. The worst weakness of these methods is that the resin is filled by the rotation of a roller and using a mask, and the residual resin is then removed by a scraper or a blade, and therefore this technique only provides a extremely weak filling force. In this method, a range of a half of a roller 30 contributes to the filling, and the other half interfere with the resin fill. To compensate for this, Japanese Patent Application Laid-Open Publication No. 2001-232758 performs an application of air pressure, but the distance involved is long, and there is a change also in an amount of resin, and high viscose resin does not react uniformly. As a whole, this leads to a considerable large-scale device, and therefore, it is difficult to be applied to a vacuum device.
Further, describing these systems with reference to FIGS. 16(A) and 16(B), the perforated plate (mask) 1 and the roller 30 are adjacent to each other so as to stop and fill a resin m. In case a filling is made into a wide space of the perforated plate 1 or the work 2, the resin m only circulates around the roller 30 as indicated by an arrow mark 30x or an arrow mark 30y, and has an extremely great defect, which does not contribute to the filling.
According to Japanese Patent Application Laid-Open Publication No. 2001-232765, the difference between a force for pulling back the resin m by the rear part of the roller and a whole pressurization of the resin m becomes an inner pressure, and when this inner pressure is increased, the resin m cannot be stopped by the scraper, but pushed back and thickly printed. Even when the space to be filled is small, a most part of the resin contributes to the filling, but since the force of pulling back the resin m in the midst of being filled gains in strength, a strong filling cannot be achieved, and there is no way to control a print shape.
Japanese Patent Application Laid-Open Publication No. 10-34878 has also an advantage of contributing to the force of filling the half of the roller in a small space, but it is weak, and the resin is pulled back by the rear portion of the roller 30, and the pressure between a rear portion blade and the rear portion of the roller 30 is unstable, and is unable to control the print shape. Further, the printing method having the above described blade and scrapper shape has a defect in that, when a printing is directly made on the substrate formed by resist, the resist is broken and peeled off. A method by a perforated plate system in the bump formation in which the miniaturizations progressed has reached critical limit, and the majority of methods are turning into the system in which a pattern is formed by resist. There is a demand for a basic factor innovation capable of precisely printing either in flatness or convexity by a strong filling force directly on a work which requires a space by various shapes.
According to Japanese Patent Application Laid Open Publication No. 2001-232758 the periphery of the roller is wrapped by a solid frame, and the replacement of the resin is extremely difficult. This device has to be disassembled and cleaned. In recent years, even the type of solder alone has come to have a great choice. Further, this device is required to be subjected to resin sealing and various types of hole-plugging, but a crucial point of the practical application thereof is whether or not the replacement of the resin can be simply performed with a minimum possible solution. The structure of the device has to be such that a portion which contacts the resin has a squeegee simply removable with a piece of roll left and can be easily cleaned.
Furthermore, since the periphery of the roller is completely sealed, this system takes air even at the boundary between the mask and the scraper. Also according to Japanese Patent Application Laid-Open Publication No. 34878, when the substrate formed with the vias by various methods such as resist and the like is filled with the solder paste, the air inside the vias is taken into the resin, and the resin continues to rotate around the roller, and the solder paste containing large quantities of void accumulated in proportion to the travel distance is fed. Even when the resin is filled, the quantity of solder is reduced, and a precise bump is not produced, and void is also contained inside the solder. Further, the recent solder has become miniaturized in a ball and extremely prone to oxidation, and this creates a great problem for melting of the solder in the subsequent working process.
Further, according to the above described vacuum differential pressure printing method, in the printing process for pressing and filling a plastic material m into the work piece 2, since the plastic material strongly adheres to the work piece 2 and the perforated plate 1, in the process for separating the perforated plated 1 from the work piece 2, it becomes difficult to separate this plastic material. In this way, there arises a problem that the adhering plastic material m hangs down from the perforated plate 1 while adhering to the perforated plate 1 and the shape of an encapsulated portion (package) crumbles.
To be more in detail, as shown in FIG. 17(A), in case a perforated plate printing method is executed by using a high viscose plastic material m such as resin and the like, the plastic material m adheres to the perforated plate 1 and the work piece (circuit board) 2, and when the work piece 2 is separated from the perforated plate 1, the periphery of the encapsulated portion comprising the plastic material m which forms the encapsulated portion is pulled. In this way, the end portion of the encapsulated portion comprising the plastic material m becomes thick, and its vicinity becomes thin, thereby generating an unevenness in thickness. Furthermore, since the plastic material m hung from the perforated plate 1 adheres to the lower surface of the perforated plate 1 due to a reaction of cutting or drops down to the work piece 2, every time this printing method is executed, the cleaning of the perforated plate 1 or the work piece 2 becomes indispensable. Further, this becomes a main cause of varying the quantity of the plastic material m fed to this print.
Further, as shown in FIG. 17(B), to flatten the encapsulated portion having the above described thickness unevenness, though an attempt is made to allow this portion to be left in the atmospheric air for a definite period of time, when the plastic material m becomes a low viscose type in the midst of being cured, there arises a problem that the material m starts flowing out and the shape of the encapsulated portion crumbles. As a countermeasure against this problem, the flowing out of the plastic material m is reduced by a cavity down system or an attempt is made to prepare a dam-shaped gate for regulating the flowing out of the plastic material m by the dispenser and the like, but there arises a problem that the production process thereof is complicated.
In the bump formation of the solder, the viscosity of the solder paste is extremely high, and there are various filling methods proposed. However, because of shifting to a narrow pitch, the aspect ratio becomes large, and a difference between the adhering force of the solder paste filled to the work piece 2 and the adhering force by the area of the side wall becomes small so that a transcription becomes extremely unstable, and there are often the case where the resin comes off from the perforated plate, the case where the resin comes off with a part thereof left, and the case where the resin does not come off at all. These cases are compensated by countermeasures such as the improvement of a shape of the hole of the perforated plate, the improvement of a surface coarseness, and the reduction of a viscosity of the coating of the mold release material. But, it is now required that solder past is not remained in the perforated plate. This is a method of dispensing the solder paste filled in the hole of the perforated plate.
To deal with the miniaturization, though there is a method executed in which a mask is prepared by a resist on the wafer substrate or the resin substrate, and the solder is filled by the atmospheric printing and reflows into the vias so as to remove the resist, when the atmospheric printing is made on blinded vias, the air remains within the interior so that the filling quantities become insufficient. Further, an amount of air proportional to the travel distance is accumulated in a solder during printing so that the quantity of solder becomes insufficient. Moreover, since the squeegee is used, the solder is scooped out by the viscosity of the resin, and is printed in a concave shape so that the quantity of solder becomes insufficient. As a result, there arises a problem of bump accuracy being lowered. Further, this results in the generation of void within the bump. Hence, a method of performing a fixed quantity filling by a voidless solder resin is desired.